The present invention generally relates to packaging and more particularly to a method and apparatus for making unitary packages which hold a plurality of components, each package containing a load wrapped in a web of stretched material.
Case packing or boxing is a common way of shipping multiple unit products. The multiple unit products are generally stacked in a corrugated box or are wrapped with kraft paper with the ends of the kraft paper being glued or taped. Another way of shipping such products is by putting a sleeve or covering of heat shrinkable film around the products and shrinking it to form a unitized package. The use of heat shrinkable film is described in U.S. Pat. Nos. 3,793,798; 3,626,654; 3,590,509 and 3,514,920. A discussion of this art is set forth in U.S. Pat. No. 3,867,806.
The present invention provides a simple, reliable and inexpensive machine and method of unitizing multiple unit products into a single wrapped package with a stretched overwrap material.
When the present process and apparatus is compared with other apparatus and processes currently used to pack products in corrugated boxes and the cost of the corrugated boxes themselves, the invention shows an enormous cost savings. The invention has comparable costs with kraft wrap but it gives a much tighter and better unitized package than that possible with kraft wrap. In addition to these factors the invention is designed to use a stretch cling type film material, which provides product visibility not possible with kraft or corrugated wrapping plus a desirable feature eliminating the heat seal required in other kinds of stretch wrapping apparatus. Furthermore, the present inventive system offers packaging speed, reliability of package seal and energy savings in that less energy is required to package the products.
A basic problem with shrink and non-cling stretch film packaging is that the primary strength and reliability of the package is determined by the consistent quality of the seal. These seals depend on a careful maintenance of the sealing jaw and are never as strong as the film itself. The time that it takes to make the seals is a limiting factor on the possible speeds of most shrink systems and a consideration in stretch systems.
The present invention does not require a structural seal and therefore can use any type of stretchable material. The invention is designed to function with a stretchable plastic cling material such as P.V.C. or cling polyethylene. In the invention the apparatus utilizes a single mechanism which effectively cuts and secures the trailing edge of the film web to the underlying film wrap. Furthermore the invention can be used with a full web application or a spiral wrap application.
The use of spiral wrapping machinery is well known in the art. One such apparatus is shown by U.S. Pat. No. 3,863,425 in which film is guided from a roll and wrapped around a cylindrical load in a spiral configuration. A carriage drives the film roll adjacent the surface of the load to deposit an overlapping spiral wrap around the load and return in the opposite direction to deposit another spiral overwrap around the load. Other spiral wrapping apparatus are described by U.S. Pat. Nos. 3,857,486; 3,788,199; 3,549,017; 3,412,524, 3,191,289 and 2,716,315. The previously indicated patents rely on heat shrink material, adhesives, a heat seal or the tacky nature of the film to hold the outer layer of wrap in a fixed position.
The use of full web wrapping machinery is also known in the art. A full web stretch wrapping apparatus using a rotatable turntable is described in U.S. Pat. No. 3,867,806. Other full web wrapping apparatus are disclosed by U.S. Pat. Nos. 3,514,920; 3,793,798; 3,795,086 and 3,986,611. In this regard it should be noted U.S. Pat. No. 3,986,611 uses a tensioned cling film while U.S. Pat. No. 3,975,086 uses a tacky P.V.C. film.
The turntable clamping assembly disclosed in this specification is disclosed in U.S. Pat. No. 4,077,179.
Various patents have described the use of mehanisms for handling wrapping materials. In U.S. Pat. No. 3,003,297 a complex cutting and holding mechanism is used to place tape on a box and cut it off with the process being repeated for each box. The use of adhesive on the tape to bond it to the package is an integral part of the function of this concept. Without this adhesion it would not work either in single, multiple or spiral configurations. The unique design and function of the clamping and sealing mechanism in the present invention does not require a heat seal of the film in order for the system to operate.
U.S. Pat. No. 2,088,133 discloses a reverse wrapping wire tying machine. In the reference a gripper mechanism holds a band in position with respect to the load to be wrapped and a rotatable ring drive rotates the band around the load until the band has completed more than one wrap of the load and passes over the body of the gripper. A separator slide is used to separate the leading edge of the band from the underlying band and a second gripper mechanism attaches to the separated band. A heat sealing mechanism welds the wrapped layer band to the band underneath it and a cutting mechanism severs the leading edge of the band held by the second gripper mechanism which then becomes the trailing edge of the succeeding wrap. When the band is severed the ring drive mechanism is rotated in a reverse direction for the following load with the various gripping and cutting mechanism functioning in the same manner.
Additional references of interest which are pertinent to rotatable drives for wrapping packages are disclosed in U.S. Pat. Nos. 3,820,451, 3,331,312, 3,324,789, 3,309,839, 3,207,060, 2,743,562, 2,639,751, 2,330,629, 2,054,603 and 2,124,770.
The present invention uses stretchable plastic cling film in its preferred embodiment since the stretched cling film can be brush sealed to hold the wrap without the necessity of a heat seal. The elasticity of the cling film holds the products under more tension than either the shrink wrap or the kraft wrap particularly with products which settle or relax when packaged.
Various other apparatus and processes owned by the assignee utilize stretch material in package wrapping. Such apparatus and processes are disclosed in U.S. Pat. Nos. 3,867,806, 4,050,220, 4,077,179 and 4,079,565.
Additional benefits occur in the present invention over the prior art in that no changeover is required in handling random size units of a variety of materials as the apparatus is constructed to handle such random size units. Furthermore, the apparatus provides a substantially continuous wrapping operation so that loads can be wrapped at any desired speed and for any time period. A significant economic factor is also present in the present invention as the power requirements are significantly less than those of shrink systems since there is no heat tunnel required and greater speeds of operation are possible because of the elimination of the conventional heat seal which is used in noncling wrapping. Furthermore a wider number of products can be handled by the present invention because of the elimination of the heat seal requirement. Because of the simplicity of the construction of the invention there is a greater stability in the inventive wrapping apparatus with less maintenance being required to maintain the apparatus resulting in a corresponding reduction in breakdown time. Another desired characteristic resulting from the apparatus construction is that the invention does no take up much floor space and can be used with either full web or spiral wrapping applications.